The invention relates to a method for producing a rotor of a fan by applying lamellae to support disks and to such a rotor for a fan.
Rotors of the type described here are known. They comprise support disks and blade lamellae, for which receiving openings are formed in the support disks. To increase the section modulus of bending and torsion, it is known to equip the rotor with a continuous shaft for absorbing the drive forces. The shaft, which is arranged in the interior of the rotor and therefore in the air-flow path, affects the flow of air inside the rotor, with the result that the volumetric flow characteristic is undesirably affected and the efficiency of the cross-flow fan is reduced. Furthermore, rotors which have support disks and blade lamellae but do not have continuous shafts are known. In these rotors, at least one of the support disks, or alternatively a casing which accommodates the rotor, is provided with a bearing journal for holding the rotor in a rotationally movable manner, which journal can be connected to a drive of the cross-flow fan.
To connect the lamellae to the support disks, it is known to weld or solder the lamellae to the support disks. Furthermore, it is known to provide two support disks, which bear against one another and through the receiving openings (which are in the shape of a segment of a circle or a crescent) of which the lamellae are fitted, with holes which are offset with respect to one another and into which rivets are introduced, so that the support disks are displaced with respect to one another and, as a result, the lamellae are held clamped in the receiving openings. Threading the lamellae into the receiving openings has proven difficult. Moreover, it is known to deform the support disk on its circumference with the aid of rollers, in such a way that the play of the joint between the receiving opening and the lamella which has been fitted in is reduced until the lamella is held clamped in the receiving opening. In this form of clamped attachment, the lamella is not deformed, but rather only the support disk is deformed, so that even after the lamellae have been connected to the support disks the lamellae retain their cross-sectional profile which they possessed prior to joining. Moreover, it remains the case that there is only a force fit between the lamellae and the support disks. A drawback of all the known variants for connecting the lamellae to the support disks is that these methods are relatively complex and therefore expensive. Furthermore, it has been found that, with these methods for clamping the lamellae in place, in some cases not all the lamellae are clamped in sufficiently, and consequently they tend to rattle at least in some operating phases of the cross-flow fan.
Therefore, the object of the invention is to provide a rotor and a method for producing the rotor which do not have these drawbacks.
To achieve this object, a method is proposed that firstly the lamellae be pushed axially into the receiving openings in the support disks, and then the profile height of each lamella be increased by plastic deformation thereof in the region of the receiving opening, so that the lamella becomes clamped in its receiving opening. In this context, it is particularly advantageous that it is possible to achieve high tolerances between the receiving opening and the lamella, so that the lamella is easy to push axially into the receiving openings during assembly. As a result of the profile height being increased, it is also possible to compensate for high levels of play between the receiving opening and lamella in an advantageous way and to produce a form- and force-fitting connection between lamella and support disk. In an advantageous variant, the receiving openings for the lamella are designed in the shape of a sickle, making it possible to produce tighter tolerances (joint play) and therefore enabling the lamellae to bear more reliably against the edge of the receiving openings that with receiving openings which are in the shape of a segment of a circle or a crescent, as provided in the known rotors. The increase in the profile height of each of the lamellae with a curved cross-sectional profile also leads to an improvement in the stiffness properties, i.e. the section modulus of bending and torsion, of the rotor, since the height of the arch of the curved lamella is reflected in the section modulus to the third power.
In an advantageous embodiment of the method, the plastic deformation of the lamella takes place adjacent to at least one side, preferably to both sides, of the support disk. As a result, a region of the lamella which is arranged in the air flow path and is preferably only small is also locally deformed to a limited extent, in order to clamp the lamella in the receiving opening in the support disk. Although the locally limited change in the cross-sectional profile of the lamella which is associated with the deformation of the lamella affects or reduces the volumetric flow characteristic and the efficiency of the fan, preferably only slightly, the advantages which result from the increase in the curvature height, such as for example the increase in the stiffness of the rotor, far outweigh this problem.
Moreover, a preferred embodiment of the method is distinguished by the fact that, for the plastic deformation, the lamellaxe2x80x94as seen in cross sectionxe2x80x94is subjected to deformation forces on its convex top side in its two edge regions and on its underside in its central zone. In this way, it is advantageously possible to achieve a form- and force-fitting three-point clamping or three-point support for the lamella at the edge of the receiving opening. This secure clamping of the lamella in the receiving opening enables high moments of resistance to be achieved by the rotor, which is advantageous in particular for the rotors of cross-flow fans, which have an unsupported structure and therefore do not have a continuous drive shaft.
To achieve the object, a rotor for a fan is also proposed wherein the rotor comprises at least two support disks which are arranged at a distance from one another, and a plurality of lamellae which pass through receiving openings in the support disks, each have a curved cross-sectional profile and are held clamped in the receiving openings. The rotor, preferably for a cross-flow fan, a radial fan or a cylindrical rotor, is distinguished by the fact that each lamella, as a result of plastic deformation which increases its profile height in the region of each support disk, is supposed on the edge of the receiving opening. As a result of this design, i.e. the increase in the curvature height of the lamellae in the region of the corresponding support disk, it is possible to increase the stiffness or elasticity properties of the rotor, in particular the section modulus to bending and torsion. In the context of the present invention, a xe2x80x9csupportxe2x80x9d for the lamella in the receiving opening is understood to mean that the lamella, which consists of a material with a certain elasticity, is deformed beyond the elastic limit, in such a manner that the lamella is pressed onto a plurality of points and/or surfaces on the edge of the receiving opening. The increase in the profile height therefore results in the lamella becoming wedged in the receiving opening.
An exemplary embodiment of the rotor in which the support is a three-point support is also preferred. In this context, the term xe2x80x9cpointxe2x80x9d is understood to mean not only punctiform contact between the lamella and the edge of the receiving opening, but also surface-to-surface contact, it being possible, for example, for surface-to-surface contact to be present at only one location of the three-point support, while at the other two bearing regions the contact is punctiform. The three-point support makes it possible to prevent the lamellae from becoming tilted or twisted in the receiving opening, which can lead to disturbing noise.
According to a refinement of the invention, stamped elevations, which bear against at least one side, preferably against both sides, of each support disk, are produced by the deformation forces for the plastic deformation. On the side which lies opposite a side of the lamella which has a stamped elevation, a recess in the form of a hollow suitably matched to the stamped elevation is formed after the deformation operation. These stamped elevations result in the support disk being held clamped between the stamped elevations, so that a relative movement of the lamella at least in the axial direction of the receiving opening in the support disk is prevented and the lamella is thus held captively.
Moreover, in a preferred exemplary embodiment of the rotor, the edge of the receiving opening cuts into the edge regions of the lamella so as to form an undercut. The fact that the edge cuts into the lamella at its edge regions adjoining the receiving opening means that lugs or deformed regions of the lamella which serve as lugs are formed, being folded or simply bent over in such a manner that the undercut is formed. As a result of these edge regions of the lamella being bent over, the latter is fixed in the receiving opening in the axial direction of the receiving opening, i.e. is held nondisplaceably in this direction.
Finally, another exemplary embodiment of the rotor which is preferred is one in which opposite zones of the edge of the receiving opening are deformed in opposite directions, transversely with respect to the plane of the support disks, in order to increase the clamped-in length of the lamella. The section modulus, i.e. the stiffness of the rotor, can be increased by a large clamped-in length. In an advantageous refinement of the invention, those zones of the edge of two receiving openings which adjoin one another are also deformed in opposite directions, transversely with respect to the plane of the support disks. The deformed edge zones of the receiving opening, which form recesses or elevations on the side faces of the support disks, are arranged alternately, i.e.xe2x80x94when only one of the side faces of the support disks is consideredxe2x80x94a hollow recess is arranged between two elevations or an elevation is arranged between two recesses.